This invention relates to a feeder, which is used on traditional wood-working machines, such as spindle modulers, circular saws, band saws, and surface planers, etc., having a speed change mechanism, and more particularly to a feeder having a speed change mechanism with a graduated threaded-shaft protector.
Referring to FIG. 1, a perspective view of a conventional feeder is shown. The feeder has a roller seat 1 in which three conveying rollers 2 are mounted. The conveying rollers 2 are driven to rotate at a constant speed by a motor 3 mounted on the roller seat 1. Such a feeder has a disadvantage in that the rotating speed of the conveying rollers 2 cannot be changed to accommodate the different kinds of wood to be handled. To solve this problem, an improved feeder with a speed change device 4 has been developed, as shown in FIG. 2. The speed change device 4 has a threaded control shaft 5 one end of which protrudes out from the roller seat 6 of the improved feeder. An adjusting knob 7 is connected with the protruding end of the threaded control shaft 5 so as that the rotating speed of the conveying rollers may be changed by manually rotating the adjusting knob 7. A speed indicating plate 8 is provided on the top of the adjusting knob 7 for showing the rotating speed of the conveying rollers. Referring to FIG. 3, the speed indicating plate 8 has a spiral line which has a plurality of numbers graduated thereon. To read the correct speed value, a user must remember the number of turns he/she has made of the adjusting knob 7 with reference to a reference mark and then compare this number with the number at the corresponding turn on the spiral line. This requires much work and is messy. In addition, foreign matter, such as wood debris, sand and dust, is likely to accumulate on the protruding end of the threaded control shaft 5, thus causing wear of said threaded control shaft 5. This wear eventually leads to both the loosening and breakage of the threaded control shaft 5.